One of the most important factors in the survival of cancer is detection at an early stage. Clinical assays that detect the early events of cancer offer an opportunity to intervene and prevent cancer progression. With the development of gene profiling and proteomics there has been significant progress in the identification of molecular markers or “biomarkers” that can be used to diagnose and prognose specific cancers. For example, in the case of prostate cancer, the antigen PSA (for prostate specific antigen) can be detected in the blood and is indicative of the presence of prostate cancer. Thus, the blood of men at risk for prostate cancer can be quickly, easily, and safely screened for elevated PSA levels.
Even though there has been significant progress in the field of cancer detection, there still remains a need in the art for the identification of new biomarkers for a variety of cancers that can be easily used in clinical applications. For example, to date there are relatively few options available for the diagnosis of breast cancer using easily detectable biomarkers. Overexpression of EGFR, particularly coupled with down-regulation of the estrogen receptor, is a marker of poor prognosis in breast cancer patients. Other known markers of breast cancer include high levels of M2 pyruvate kinase (M2 PK) in blood (U.S. Pat. No. 6,358,683), high ZNF217 protein levels in blood (WO 98/02539), and differential expression of a newly identified protein in breast cancer, PDEBC, which is useful for diagnosis (U.S. patent application No. 20030124543). Cell surface markers such as CEA, CA-125 and HCG are frequently elevated in the serum of patients with locally advanced and metastatic bladder cancer (Izes et al., J. Urol. June; 165(6 Pt 1):1908-13, 2001), and studies involving circulating levels of tumor-related proteins such as matrix metalloproteinase-2 (Gohji et al., Cancer Research 56:3196, 1996), hepatocyte growth factor (Gohji et al., J. Clin. Oncol. 18:2963, 2000), and tissue polypeptide antigen (Maulard-Durdux et al., J. Clin. Oncol. 15:3446, 1997) have shown promise. These biomarkers offer alternative methods of diagnosis, however, they are not widely used. Furthermore, despite the use of a number of histochemical, genetic, and immunological markers, clinicians still have a difficult time predicting which tumors will metastasize to other organs.
The identification of cancer biomarkers is particularly relevant to improving diagnosis, prognosis, and treatment of the disease. As such, there is need in the art to identify alternative biomarkers that can be quickly, easily, and safely detected. Such biomarkers may be used to diagnose, to stage, or to monitor the progression or treatment of a subject with bladder cancer, in particular, an invasive, potentially metastatic stage of the disease.